1. Field of Invention
The invention relates to a wiper arm of a wiper apparatus for wiping off adherents on a window surface of an automobile or other vehicle.
2. Description of Related Art
Such a wiper arm typically comprises a base portion which is secured to a wiper shaft in an automobile body so as to be connected to an arm head thereto swingably and a top portion of the arm head which holds a wiper blade for wiping a window surface. A conventional wiper arm is formed of an arm shank as the base portion having a substantially H-shaped cross-section and an arm piece as the top portion having a narrow flat-plate shape for affixing the wiper blade, and both parts are separately formed to be connected to each other by securing means, such as by riveting. However, there has been a problem in such a wiper arm in that a difference in level occurs between an arm shank section and an arm piece section thereby not only ruining the design, but also increasing the number of parts, which reduces assembly efficiency. Therefore, unitarily forming the arm shank and the arm piece has been proposed, for example, in JP-U-4-34160.
In this case, the wiper arm is formed by bending a plate-shaped material. That is, side-pieces continuing from both sides of the arm shank are folded to abut the bottom-piece portion so as to form the arm piece having a substantially flat-plate shape.
Also, the wiper arm must have a spring device interposed between the arm shank and the arm head so that the top portion to which the wiper blade is attached is urged toward the window surface. In the above-described example, a plate for receiving the spring device is sandwiched between both side pieces and the bottom piece in the base portion side of the arm piece, and the spring device is attached thereto via the plate, so that the load of the spring device acting on the arm piece is received on the portion reinforced by the plate. However, since a region, in which both side pieces are simply bent (crushed) so as to be folded over to abut the bottom-piece portion in a flat shape is formed between the portion for attaching the wiper blade in the top portion of the arm piece and the portion in which the above-mentioned plate is clamped, the strength of this region is lower than that of the clamping portion of the plate. Therefore, in the region where is not clamped by the plate or a boundary portion between the region and the clamped portion, the wire arm itself is prone to be bent when a large load is exerted on the wiper blade. There is a problem therein to be solved by the invention.
Accordingly, the invention has been made so as to solve the problem. A wiper arm for affixing a wiper blade thereto for wiping a window surface, the wiper arm comprising a base end portion formed to have a II-shaped cross-section opening toward the window surface by bending a flat plate; and a top end portion formed by folding back sides of the flat plate continuously from the base end portion, wherein the thickness of the top end portion in a folded state is set to be equal to or more than twice the thickness of the flat plate.
With these features, the rigidity of the wiper arm in the longitudinal direction of the arm is improved.
In a wiper arm according to the invention, the top end portion of the wiper arm is set to be more than twice the thickness of the flat plate by laterally curving a bottom-piece portion of the top end portion opposing the surface.
Furthermore, in a wiper arm according to the invention, the top end portion of the wiper arm is formed to have a thickness more than twice the thickness of the flat plate by forming a gap between the bottom-piece portion of the top end portion and folded-piece portions on both sides.
In a wiper arm according to the invention, preferably, the top end portion of the wiper arm is formed to have a thickness more than twice the thickness of the flat plate by respectively bending folded-piece portions into a cylindrical shape.
Furthermore, in a wiper arm according to the invention, the thickness of the top end portion of the wiper arm is set to be more than twice the thickness of the flat plate, except for a portion for attaching the wiper blade at an extreme end portion of the top end portion.
Still furthermore, in a wiper arm according to the invention, preferably, notch portions for admitting and draining coating liquid are formed at opposing edge portions, opposing each other, of the folded-piece portions.